Abstract: The goal of this RO1 application is to continue the research on antiretroviral nanoparticles (AR NPs) based on the previous R15 award. Antiretroviral nanoparticles containing ritonavir, lopinavir, and efavirenz have been able to show success as a sustained drug delivery system. This application is designed to answer several questions regarding dissemination of AR NPs, efficacy in a mouse model of HIV-1 and finally, efficacy associated with macaques. Specific Aim 1 will determine the dissemination of fluorescent NPs using a small animal fluorescent imager and nude mice as the model system. This model will also determine length of time these NPs remain in specific areas of the body. A 2nd Specific Aim is to determine the most appropriate dose and route of administration of AR NPs using the Rag2-/-gamma interferon-/- double knockout mouse model of HIV-1. These mice will be reconstituted with human CD34 cells, infected with HIV, and then administered AR NPs at pre-defined intervals. The animals will be sacrificed after specific times to determine amount of HIV-1 virus, CD4/CD8 human cells within both plasma and spleen. These values will be compared to mice that receive HIV-1 and blank NPs. Finally, we would like to collaborate with Drs. Jason Kimata and Marie-Claire Gauduin at Baylor College of Medicine and Southwest National Primate Research Center, respectively to determine the most appropriate dose and route of administration of AR NPs in a pigtail macaque model of HIV- 1 infection using RT-SHIVmne. We are proposing that four animals undergo a pilot pharmacokinetic study to determine the most appropriate dose and route of administration of the AR NPs based on the HIV-1 mouse model experiments. Then these macaques and four additional pigtail macaques will be infected with RTSHIVmne. Four macaques will serve as control animals and four will receive AR NPs. Blood and lymph node biopsies will be harvested at specific times to determine immunological and virological analyses. Animals will receive AR NPs every 4 weeks for a minimum of 20 weeks. Animals will stop receiving AR NPs and plasma will be checked weekly to determine virologic and immunologic status. AR NPs animals will receive additional doses of AR NPs at every 4-weekly dosage if virologic studies meet a define threshold. Animals will be euthanized and necropsy will be performed to determine if the AR NPs affect viral reservoirs. Determination of resistant populations of HIV-1 will be performed (Specific Aim 3). It is our intention to determine whether these AR NPs are able to impact HIV-1 viral loads, CD4/CD8 cell counts, viral reservoirs, and resistance in animal models of HIV-1. This will be the first step to determine the utility of AR NPs as a treatment option suitable for human use.